Embodiments described herein relate generally to electrochemical cells having semi-solid electrodes that include a polymer additive such that the electrodes demonstrate better physical properties and longer cycle life while significantly retaining the electronic performance of the electrodes and the electrochemical cells formed therefrom.
Electrochemical cells or batteries are typically constructed of solid electrodes, separators, electrolyte, and ancillary components such as, for example, packaging, thermal management, cell balancing, consolidation of electrical current carriers into terminals, and/or other such components. The electrodes typically include active materials, conductive materials, binders and other additives.
Conventional methods for preparing electrochemical cells generally include coating a metallic substrate (e.g., a current collector) with slurry composed of an active material, a conductive additive, and a binding agent dissolved or dispersed in a solvent, evaporating the solvent, and calendering the dried solid matrix to a specified thickness. The electrodes are then cut, packaged with other components, infiltrated with electrolyte and the entire package is then sealed.
Such known methods generally involve complicated and expensive manufacturing steps such as casting the electrode and are only suitable for electrodes of limited thickness, for example, less than 100 μm (final single sided coated thickness). These known methods for producing electrodes of limited thickness result in batteries with lower capacity, lower energy density and a high ratio of inactive components to active materials. Furthermore, the binders used in known electrode formulations can increase tortuosity and decrease the ionic conductivity of the electrode.
Known electrochemical batteries such as, for example, lithium-ion batteries also lose their charge capacity after repeated charge and discharge cycles. Lithium-ion batteries are known to lose about 20% of their initial charge capacity after a year. This loss is attributed to many factors including, for example, internal oxidation, exposure to high temperatures, alterations in crystal structure of components included in the anode and/or cathode, gas generation, and physical wear and tear. There is a need for new electrochemical batteries that do not lose charge capacity or do so at a much lower rate such that they have longer cycle life.
Thus, it is an enduring goal of energy storage systems development to develop new electrochemical batteries and electrodes that have longer cycle life, increased energy density, charge capacity and overall performance.